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every year I come to this frastration. Here it is : I go to a n A/C maintenace call, clean condenser, check evap. coil drop, filter, static pressure (if needed) etc..... and finally I put my gauges on. I see S.L. (Suction line) pressure = 55psig, L.L. pressure 190 psig, O.A.T.(outside ambient temp) at 80F. Now, what do I do ? Is this an indication that there is leak ??? Called my boss, he said - " find the leak !" - "what leak" I ask ....

So, last week on a Bryant 2 ton, I cut both lines and installed "access valves" . Brought my Nitrogen bottle and pressured the system to 120 psig. Left the customer and came back next day. NO DARN LEAK (sorry about the CAPS), Pressure did not move at all. Nada.

Told my boss, but he still insists if the pressure on my gauges is not "text book case" - then I must find the leak. What Leak ? So, says the LAW.

Question: If the pressure on your gauges is 5-10psig LOWER than what it should be (according to O.A.T.) - what do you guys do ?

I guess the question I have first thing would be.....Do you know the past history of this unit to begin with? If it isnt a unit that I have worked on in the past, and know it had the right charge in the first place I dont spend a huge amount of time trying to find a leak. If It did have the right charge, and I know that for sure then I inform the owner that we need to spend the time and money to find it and fix it. Now if I dont know for sure there is a leak I make it the homeowners option to spend the time and money looking for a leak that may not be there or to charge it and wait and see if it looses charge from that point on. They have the option. I lean towards waiting and seeing if it looses my known charge.

Originally posted by bananaboy The company I work for, services any A/C (Furnace) installed by us or not.

Assuming the pressure was correct from the "get-go", then a drop of 10 psig 5-10years later IS or IS IT NOT normal ?

I would not assume anything but if your saying you know it was right 5-10 years ago and lost 10 psig I dont know if I would look that hard to find that leak. It should not loose any gas but that amount over 5-10 years is going to be a small leak. I would test for leaks but as far as spending hours on it, owner would have to approve that. Hundreds of dollars spent on finding a really slow leaking valve core that finally sealed is a bad idea to me lol.

You're right, I did cut the pipes and install the valve just to prove to the boss that there is NO real leak, but the "Shrader valves" were releasing a bit(may be during the winter, when the rubber shrinks).

It is really frustrating to deal with those cases, because when the heat wave comes - the A/C is not as efficient and need a bit of "shot in the arm" (R22).

Of course the SH and SC will be a bit "off" if the pressure is lower (a bit), but this is only felt when outside is 85-90 F

if TXV use SC if piston type use SH. use manufacturers specs for correct numbers. does HO have unit serviced yearly. freon is lost every time gauges put on although minimal. could explain for leak over time or just leaking schrader core as stated before. if my 1st time on call I would look for oil anywhere on system for obviuos. tell HO of unit may have small leak, and more time in future may be needed.

add charge, how much cool juice did it take, a lot-look for a leak, a little -it may be nothing or it may be a small leak, like valve cores as mentioned. sorry if i come across as snotty, i just do not let pressures bother me, IF all else is right on.

Next time take a web bulb reading, and then see if your super heat is off, if its a fixed metering device. Your indoor wb might have been low, and that will give you a lower suction pressure, and superheat.

At 60°wb, and 80° od db, your super heat would be around 8°, and with a suction line temp of 43°, a vapor pressure of 55 is ok.

By the way, its not the pressure thats off.

A 15 seer a/c doesn't have as high of a head pressure as a 10 seer.
So stop worrying about the pressure.

PS: what law says you must find and fix the leak on a system containing less then 50 lbs.

when was the last time it was serviced. or how many times was it serviced. if the tech did not use low lose hoses while checking the charge then you could lose if my memorie is right 4oz each time. i might be off a little
it is rare but there are still some guys that dont use low lose hoses. if checked 4 times there is a pound.
sounds like you are getting to involved in this if it took this long to show up. may be it was never charged properly
or checked properly. if it is a leak it is so small you will never find it